1 files changed, 530 insertions, 0 deletions
diff --git a/drivers/block/brd.c b/drivers/block/brd.c
new file mode 100644
index 000000000..a8a77a1ef
--- /dev/null
+++ b/drivers/block/brd.c
@@ -0,0 +1,530 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Ram backed block device driver.
+ *
+ * Copyright (C) 2007 Nick Piggin
+ * Copyright (C) 2007 Novell Inc.
+ *
+ * Parts derived from drivers/block/rd.c, and drivers/block/loop.c, copyright
+ * of their respective owners.
+ */
+
+#include <linux/init.h>
+#include <linux/initrd.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/major.h>
+#include <linux/blkdev.h>
+#include <linux/bio.h>
+#include <linux/highmem.h>
+#include <linux/mutex.h>
+#include <linux/pagemap.h>
+#include <linux/radix-tree.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/backing-dev.h>
+#include <linux/debugfs.h>
+
+#include <linux/uaccess.h>
+
+/*
+ * Each block ramdisk device has a radix_tree brd_pages of pages that stores
+ * the pages containing the block device's contents. A brd page's ->index is
+ * its offset in PAGE_SIZE units. This is similar to, but in no way connected
+ * with, the kernel's pagecache or buffer cache (which sit above our block
+ * device).
+ */
+struct brd_device {
+	int			brd_number;
+	struct gendisk		*brd_disk;
+	struct list_head	brd_list;
+
+	/*
+	 * Backing store of pages and lock to protect it. This is the contents
+	 * of the block device.
+	 */
+	spinlock_t		brd_lock;
+	struct radix_tree_root	brd_pages;
+	u64			brd_nr_pages;
+};
+
+/*
+ * Look up and return a brd's page for a given sector.
+ */
+static struct page *brd_lookup_page(struct brd_device *brd, sector_t sector)
+{
+	pgoff_t idx;
+	struct page *page;
+
+	/*
+	 * The page lifetime is protected by the fact that we have opened the
+	 * device node -- brd pages will never be deleted under us, so we
+	 * don't need any further locking or refcounting.
+	 *
+	 * This is strictly true for the radix-tree nodes as well (ie. we
+	 * don't actually need the rcu_read_lock()), however that is not a
+	 * documented feature of the radix-tree API so it is better to be
+	 * safe here (we don't have total exclusion from radix tree updates
+	 * here, only deletes).
+	 */
+	rcu_read_lock();
+	idx = sector >> PAGE_SECTORS_SHIFT; /* sector to page index */
+	page = radix_tree_lookup(&brd->brd_pages, idx);
+	rcu_read_unlock();
+
+	BUG_ON(page && page->index != idx);
+
+	return page;
+}
+
+/*
+ * Insert a new page for a given sector, if one does not already exist.
+ */
+static int brd_insert_page(struct brd_device *brd, sector_t sector, gfp_t gfp)
+{
+	pgoff_t idx;
+	struct page *page;
+	int ret = 0;
+
+	page = brd_lookup_page(brd, sector);
+	if (page)
+		return 0;
+
+	page = alloc_page(gfp | __GFP_ZERO | __GFP_HIGHMEM);
+	if (!page)
+		return -ENOMEM;
+
+	if (radix_tree_maybe_preload(gfp)) {
+		__free_page(page);
+		return -ENOMEM;
+	}
+
+	spin_lock(&brd->brd_lock);
+	idx = sector >> PAGE_SECTORS_SHIFT;
+	page->index = idx;
+	if (radix_tree_insert(&brd->brd_pages, idx, page)) {
+		__free_page(page);
+		page = radix_tree_lookup(&brd->brd_pages, idx);
+		if (!page)
+			ret = -ENOMEM;
+		else if (page->index != idx)
+			ret = -EIO;
+	} else {
+		brd->brd_nr_pages++;
+	}
+	spin_unlock(&brd->brd_lock);
+
+	radix_tree_preload_end();
+	return ret;
+}
+
+/*
+ * Free all backing store pages and radix tree. This must only be called when
+ * there are no other users of the device.
+ */
+#define FREE_BATCH 16
+static void brd_free_pages(struct brd_device *brd)
+{
+	unsigned long pos = 0;
+	struct page *pages[FREE_BATCH];
+	int nr_pages;
+
+	do {
+		int i;
+
+		nr_pages = radix_tree_gang_lookup(&brd->brd_pages,
+				(void **)pages, pos, FREE_BATCH);
+
+		for (i = 0; i < nr_pages; i++) {
+			void *ret;
+
+			BUG_ON(pages[i]->index < pos);
+			pos = pages[i]->index;
+			ret = radix_tree_delete(&brd->brd_pages, pos);
+			BUG_ON(!ret || ret != pages[i]);
+			__free_page(pages[i]);
+		}
+
+		pos++;
+
+		/*
+		 * It takes 3.4 seconds to remove 80GiB ramdisk.
+		 * So, we need cond_resched to avoid stalling the CPU.
+		 */
+		cond_resched();
+
+		/*
+		 * This assumes radix_tree_gang_lookup always returns as
+		 * many pages as possible. If the radix-tree code changes,
+		 * so will this have to.
+		 */
+	} while (nr_pages == FREE_BATCH);
+}
+
+/*
+ * copy_to_brd_setup must be called before copy_to_brd. It may sleep.
+ */
+static int copy_to_brd_setup(struct brd_device *brd, sector_t sector, size_t n,
+			     gfp_t gfp)
+{
+	unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
+	size_t copy;
+	int ret;
+
+	copy = min_t(size_t, n, PAGE_SIZE - offset);
+	ret = brd_insert_page(brd, sector, gfp);
+	if (ret)
+		return ret;
+	if (copy < n) {
+		sector += copy >> SECTOR_SHIFT;
+		ret = brd_insert_page(brd, sector, gfp);
+	}
+	return ret;
+}
+
+/*
+ * Copy n bytes from src to the brd starting at sector. Does not sleep.
+ */
+static void copy_to_brd(struct brd_device *brd, const void *src,
+			sector_t sector, size_t n)
+{
+	struct page *page;
+	void *dst;
+	unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
+	size_t copy;
+
+	copy = min_t(size_t, n, PAGE_SIZE - offset);
+	page = brd_lookup_page(brd, sector);
+	BUG_ON(!page);
+
+	dst = kmap_atomic(page);
+	memcpy(dst + offset, src, copy);
+	kunmap_atomic(dst);
+
+	if (copy < n) {
+		src += copy;
+		sector += copy >> SECTOR_SHIFT;
+		copy = n - copy;
+		page = brd_lookup_page(brd, sector);
+		BUG_ON(!page);
+
+		dst = kmap_atomic(page);
+		memcpy(dst, src, copy);
+		kunmap_atomic(dst);
+	}
+}
+
+/*
+ * Copy n bytes to dst from the brd starting at sector. Does not sleep.
+ */
+static void copy_from_brd(void *dst, struct brd_device *brd,
+			sector_t sector, size_t n)
+{
+	struct page *page;
+	void *src;
+	unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
+	size_t copy;
+
+	copy = min_t(size_t, n, PAGE_SIZE - offset);
+	page = brd_lookup_page(brd, sector);
+	if (page) {
+		src = kmap_atomic(page);
+		memcpy(dst, src + offset, copy);
+		kunmap_atomic(src);
+	} else
+		memset(dst, 0, copy);
+
+	if (copy < n) {
+		dst += copy;
+		sector += copy >> SECTOR_SHIFT;
+		copy = n - copy;
+		page = brd_lookup_page(brd, sector);
+		if (page) {
+			src = kmap_atomic(page);
+			memcpy(dst, src, copy);
+			kunmap_atomic(src);
+		} else
+			memset(dst, 0, copy);
+	}
+}
+
+/*
+ * Process a single bvec of a bio.
+ */
+static int brd_do_bvec(struct brd_device *brd, struct page *page,
+			unsigned int len, unsigned int off, blk_opf_t opf,
+			sector_t sector)
+{
+	void *mem;
+	int err = 0;
+
+	if (op_is_write(opf)) {
+		/*
+		 * Must use NOIO because we don't want to recurse back into the
+		 * block or filesystem layers from page reclaim.
+		 */
+		gfp_t gfp = opf & REQ_NOWAIT ? GFP_NOWAIT : GFP_NOIO;
+
+		err = copy_to_brd_setup(brd, sector, len, gfp);
+		if (err)
+			goto out;
+	}
+
+	mem = kmap_atomic(page);
+	if (!op_is_write(opf)) {
+		copy_from_brd(mem + off, brd, sector, len);
+		flush_dcache_page(page);
+	} else {
+		flush_dcache_page(page);
+		copy_to_brd(brd, mem + off, sector, len);
+	}
+	kunmap_atomic(mem);
+
+out:
+	return err;
+}
+
+static void brd_submit_bio(struct bio *bio)
+{
+	struct brd_device *brd = bio->bi_bdev->bd_disk->private_data;
+	sector_t sector = bio->bi_iter.bi_sector;
+	struct bio_vec bvec;
+	struct bvec_iter iter;
+
+	bio_for_each_segment(bvec, bio, iter) {
+		unsigned int len = bvec.bv_len;
+		int err;
+
+		/* Don't support un-aligned buffer */
+		WARN_ON_ONCE((bvec.bv_offset & (SECTOR_SIZE - 1)) ||
+				(len & (SECTOR_SIZE - 1)));
+
+		err = brd_do_bvec(brd, bvec.bv_page, len, bvec.bv_offset,
+				  bio->bi_opf, sector);
+		if (err) {
+			if (err == -ENOMEM && bio->bi_opf & REQ_NOWAIT) {
+				bio_wouldblock_error(bio);
+				return;
+			}
+			bio_io_error(bio);
+			return;
+		}
+		sector += len >> SECTOR_SHIFT;
+	}
+
+	bio_endio(bio);
+}
+
+static int brd_rw_page(struct block_device *bdev, sector_t sector,
+		       struct page *page, enum req_op op)
+{
+	struct brd_device *brd = bdev->bd_disk->private_data;
+	int err;
+
+	if (PageTransHuge(page))
+		return -ENOTSUPP;
+	err = brd_do_bvec(brd, page, PAGE_SIZE, 0, op, sector);
+	page_endio(page, op_is_write(op), err);
+	return err;
+}
+
+static const struct block_device_operations brd_fops = {
+	.owner =		THIS_MODULE,
+	.submit_bio =		brd_submit_bio,
+	.rw_page =		brd_rw_page,
+};
+
+/*
+ * And now the modules code and kernel interface.
+ */
+static int rd_nr = CONFIG_BLK_DEV_RAM_COUNT;
+module_param(rd_nr, int, 0444);
+MODULE_PARM_DESC(rd_nr, "Maximum number of brd devices");
+
+unsigned long rd_size = CONFIG_BLK_DEV_RAM_SIZE;
+module_param(rd_size, ulong, 0444);
+MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes.");
+
+static int max_part = 1;
+module_param(max_part, int, 0444);
+MODULE_PARM_DESC(max_part, "Num Minors to reserve between devices");
+
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_BLOCKDEV_MAJOR(RAMDISK_MAJOR);
+MODULE_ALIAS("rd");
+
+#ifndef MODULE
+/* Legacy boot options - nonmodular */
+static int __init ramdisk_size(char *str)
+{
+	rd_size = simple_strtol(str, NULL, 0);
+	return 1;
+}
+__setup("ramdisk_size=", ramdisk_size);
+#endif
+
+/*
+ * The device scheme is derived from loop.c. Keep them in synch where possible
+ * (should share code eventually).
+ */
+static LIST_HEAD(brd_devices);
+static struct dentry *brd_debugfs_dir;
+
+static int brd_alloc(int i)
+{
+	struct brd_device *brd;
+	struct gendisk *disk;
+	char buf[DISK_NAME_LEN];
+	int err = -ENOMEM;
+
+	list_for_each_entry(brd, &brd_devices, brd_list)
+		if (brd->brd_number == i)
+			return -EEXIST;
+	brd = kzalloc(sizeof(*brd), GFP_KERNEL);
+	if (!brd)
+		return -ENOMEM;
+	brd->brd_number		= i;
+	list_add_tail(&brd->brd_list, &brd_devices);
+
+	spin_lock_init(&brd->brd_lock);
+	INIT_RADIX_TREE(&brd->brd_pages, GFP_ATOMIC);
+
+	snprintf(buf, DISK_NAME_LEN, "ram%d", i);
+	if (!IS_ERR_OR_NULL(brd_debugfs_dir))
+		debugfs_create_u64(buf, 0444, brd_debugfs_dir,
+				&brd->brd_nr_pages);
+
+	disk = brd->brd_disk = blk_alloc_disk(NUMA_NO_NODE);
+	if (!disk)
+		goto out_free_dev;
+
+	disk->major		= RAMDISK_MAJOR;
+	disk->first_minor	= i * max_part;
+	disk->minors		= max_part;
+	disk->fops		= &brd_fops;
+	disk->private_data	= brd;
+	strscpy(disk->disk_name, buf, DISK_NAME_LEN);
+	set_capacity(disk, rd_size * 2);
+	
+	/*
+	 * This is so fdisk will align partitions on 4k, because of
+	 * direct_access API needing 4k alignment, returning a PFN
+	 * (This is only a problem on very small devices <= 4M,
+	 *  otherwise fdisk will align on 1M. Regardless this call
+	 *  is harmless)
+	 */
+	blk_queue_physical_block_size(disk->queue, PAGE_SIZE);
+
+	/* Tell the block layer that this is not a rotational device */
+	blk_queue_flag_set(QUEUE_FLAG_NONROT, disk->queue);
+	blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, disk->queue);
+	blk_queue_flag_set(QUEUE_FLAG_NOWAIT, disk->queue);
+	err = add_disk(disk);
+	if (err)
+		goto out_cleanup_disk;
+
+	return 0;
+
+out_cleanup_disk:
+	put_disk(disk);
+out_free_dev:
+	list_del(&brd->brd_list);
+	kfree(brd);
+	return err;
+}
+
+static void brd_probe(dev_t dev)
+{
+	brd_alloc(MINOR(dev) / max_part);
+}
+
+static void brd_cleanup(void)
+{
+	struct brd_device *brd, *next;
+
+	debugfs_remove_recursive(brd_debugfs_dir);
+
+	list_for_each_entry_safe(brd, next, &brd_devices, brd_list) {
+		del_gendisk(brd->brd_disk);
+		put_disk(brd->brd_disk);
+		brd_free_pages(brd);
+		list_del(&brd->brd_list);
+		kfree(brd);
+	}
+}
+
+static inline void brd_check_and_reset_par(void)
+{
+	if (unlikely(!max_part))
+		max_part = 1;
+
+	/*
+	 * make sure 'max_part' can be divided exactly by (1U << MINORBITS),
+	 * otherwise, it is possiable to get same dev_t when adding partitions.
+	 */
+	if ((1U << MINORBITS) % max_part != 0)
+		max_part = 1UL << fls(max_part);
+
+	if (max_part > DISK_MAX_PARTS) {
+		pr_info("brd: max_part can't be larger than %d, reset max_part = %d.\n",
+			DISK_MAX_PARTS, DISK_MAX_PARTS);
+		max_part = DISK_MAX_PARTS;
+	}
+}
+
+static int __init brd_init(void)
+{
+	int err, i;
+
+	brd_check_and_reset_par();
+
+	brd_debugfs_dir = debugfs_create_dir("ramdisk_pages", NULL);
+
+	for (i = 0; i < rd_nr; i++) {
+		err = brd_alloc(i);
+		if (err)
+			goto out_free;
+	}
+
+	/*
+	 * brd module now has a feature to instantiate underlying device
+	 * structure on-demand, provided that there is an access dev node.
+	 *
+	 * (1) if rd_nr is specified, create that many upfront. else
+	 *     it defaults to CONFIG_BLK_DEV_RAM_COUNT
+	 * (2) User can further extend brd devices by create dev node themselves
+	 *     and have kernel automatically instantiate actual device
+	 *     on-demand. Example:
+	 *		mknod /path/devnod_name b 1 X	# 1 is the rd major
+	 *		fdisk -l /path/devnod_name
+	 *	If (X / max_part) was not already created it will be created
+	 *	dynamically.
+	 */
+
+	if (__register_blkdev(RAMDISK_MAJOR, "ramdisk", brd_probe)) {
+		err = -EIO;
+		goto out_free;
+	}
+
+	pr_info("brd: module loaded\n");
+	return 0;
+
+out_free:
+	brd_cleanup();
+
+	pr_info("brd: module NOT loaded !!!\n");
+	return err;
+}
+
+static void __exit brd_exit(void)
+{
+
+	unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
+	brd_cleanup();
+
+	pr_info("brd: module unloaded\n");
+}
+
+module_init(brd_init);
+module_exit(brd_exit);
+